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Soil Test Interpretation Guide

Author: Mr. Guy Sela, CEO of SMART! Fertilizer Management software and an international expert in plant nutrition and irrigation.

 

 

 

Extraction
Method

 

2N KCl

 

Bray

 

Olsen

 

Ammonium Acetate

 

Ammonium Bicarbonate - DTPA

Rating/Units ppm ppm ppm meq/100g ppm ppm
Low <20 <20 <10 <0.45 <175 <60
Adequate 20-41 20-40 10-15 0.45-0.7 175-280 61-120
High 41-75 40-100 15-40 0.7-2.0 280-800 121-180
Excessive >75 >100 >40 >2.0 >800 >180

 

  

Extraction

Method

Ammonium Acetate Ammonium Acetate KCL 40
Rating/Units meq/100g ppm meq/100g ppm ppm
Low <5 <1000 <0.5 <60 <5
Adequate 5-10 1000-2000 0.5-1.5 60-180 5-10
High >10 >2000 >1.5 >180 10-20
Excessive         >20

  

 

Extraction
Method
DTPA DTPA DTPA DTPA Hot Water
Rating/Units ppm ppm ppm ppm ppm
Low <2.5 <0.6 <1.0 <0.6 <0.5
Adequate 2.5-5.0 >2.0 >1.5 >2.0 0.5-2.0
High >5.0       >2.0

 

  

Rating 1:1 Extract EC (mmhos/cm) Saturated Paste 
ECe (mmhos/cm)
Low (Non-saline) 0.01-0.45 0.0-2.0
Low (Slightly saline) 0.45-1.5 2.1-4.0

Medium (Moderately saline)

1.51-2.9 4.01-8.0
High (Strongly saline) 2.91-8.5 8.01-16.0
Very high (Very strongly saline) >8.5 >16.0

 

 
Desirable range of exchangeable cations
Cation Range
Calcium 65%-80%
Magnesium 10%-20%
Potassium 3%-8%
Sodium <6%
Aluminium <1%


The values and ranges presented are in no way absolute. The aim is for you to use this document to get better understanding of the numbers and the terms used in soil test reports

 

Soil Test Interpretation Software

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  • Compare on charts different soil test results
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        reports.


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